How geckos stay upright

Even lizards sometimes lose their grip scrambling up sheer faces. But like a falling cat, the gecko is able to control its plunge so that it nearly always lands on all fours. A study which recorded the lizards falling on high-speed video showed the mid-air gymnastics was down to a flick of the tail. Once upright the lizards can glide to safety using their tail as a rudder.

"Air righting in mammals is characterised by a bending and twisting of the spine," said Ardian Jusufi, one of the University of California Berkeley research team.

In other tests the researchers looked at what happened when the flat-tailed house geckos of south-east Asia lost their footing on slippery vertical surfaces. Again the tail was crucial in helping regain purchase, either with a tap to the surface or by flattening it to the wall.

"When we put in a slippery patch, we found they have an active tail that functions like a fifth leg to keep them from tipping backward," said research leader Prof Robert Full. The study is published today in Proceedings of the National Academy of Sciences.